IB Biology Internal Assessment Exemplar
Investigating the Effects of Different Amounts of Potassium Chloride (KCl) on the Growth of Basil (Ocimum bascilicum) Seedlings
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Criteria A: Research Design
5/6
0
3
6
Criteria Strands
Research question clearly identifies independent and dependent variables within a specific agronomic context.
Background effectively links basil physiology and KCl fertiliser practice, justifying experimental concentrations and duration.
Methodological considerations are well explained, with discussion of key variables and rationale for replicates and timeframe.
Procedural ambiguities remain (inconsistent cup numbers, omitted time-zero measurements).
No seed viability test described to ensure uniform germination.
Volume-based KCl percentages lack conversion to mass, reducing reproducibility clarity.
Criteria B: Data Analysis
4/6
0
3
6
Criteria Strands
Raw data are comprehensively tabulated with means, standard deviations, and a scatter plot with error bars.
Appropriate statistical processing (one-way ANOVA with Tukey HSD) demonstrates sound analysis.
Clarity in descriptive statistics is shown via inclusion of skewness formula and consolidated summary tables.
Table headings and unit placement are misaligned; integer data obscure the stated ±0.05 cm uncertainty.
Uncertainties are listed but not propagated into error bars or reflected in processed results.
Minor inaccuracies in SD/skewness values and missing F-statistic/df in ANOVA reduce precision.
Criteria C: Conclusion
5/6
0
3
6
Criteria Strands
Conclusion directly answers the research question and is quantitatively supported by the statistical results (e.g., p < 0.00001).
Findings are explained using accepted physiological concepts and literature on potassium and salinity stress.
No contradictory claims are made; conclusion is consistent with all presented analysis.
Variation in SD and skewness is not addressed in the discussion of results.
Comparison to scientific context is relevant but lacks deeper critical integration with multiple sources.
Criteria D: Evaluation
3/6
0
3
6
Criteria Strands
Identifies specific methodological weaknesses (measurement error, environmental fluctuations, incomplete dissolution).
Proposes realistic improvements directly related to issues (narrower concentration intervals, longer duration).
Does not explain the relative impact or magnitude of each identified weakness.
Improvements are described but not linked in detail to how they mitigate specific limitations.